1. Field of the Invention
The present invention relates to exhaust systems and more particularly to the reduction of exhaust gas temperature without affecting operation of pollution control elements of the exhaust system.
2. Description of the Prior Art
Elevated exhaust gas temperatures from the tail pipes of diesel engine equipped motor vehicles have become a greater problem with the introduction of diesel particulate trap/filters (DPF) and the need to regenerate these filters. Diesel particulate filters remove unburned and partially burned hydrocarbons from the exhaust streams produced by diesel engines. A DPF may be periodically regenerated by raising the temperature in the filter sufficiently to accelerate the oxidation of or ignite the particulate matter trapped in the filter. This process, once initiated, further increases the temperature of the exhaust stream downstream from the filter. The increase in the temperature of the exhaust may singe passers-by, particularly where the exhaust is discharged near ground level, and add stress on exhaust pipes.
The prior art frequently, though not universally, achieved exhaust gas cooling as a byproduct of cooling a component, such as a muffler, in the exhaust system. In some contemporary pollution control schemes components of the exhaust gas treatment system must run hot in order to operate or regenerate making it undesirable to reduce exhaust gas temperature ahead of the component in question or to reduce the temperature of the component itself. For example, diesel particulate filter regeneration requires maintaining the temperature of the filter during regeneration.
There is thus a need to cool the exhaust gas after the exhaust leaves the filter. It remains desirable to protect pipes of the exhaust system from the high temperatures which attach to the casing housing the filter as well as reduce the danger of singing passers-by.
Reducing the exhaust gas temperature after leaving the diesel particulate filter can be accomplished with a temperature control device. The temperature control device typically has inlets that allow fresh air into the device can form a venturi to mix the exhaust gas with the air.
While this device works well to reduce the temperature of the exhaust, some exhaust can escape from the system if the tail pipe is clogged or plugged. Because the exhaust gasses are hot, they could potentially burn someone walking by. Furthermore, if the inlets in the device become blocked with debris or by other equipment, the temperature of the exhaust will rise above acceptable levels.
Therefore, there remains a need to reduce the temperature of the exhaust gas without allowing the exhaust gas to escape out of the temperature control device, especially if the end of the exhaust pipe is plugged. There is also a need to prevent the inlets of the device from becoming blocked. In addition, there is a need to further reduce the temperature levels of the exhaust.